java50题----27求素数

/*求100之内有多少个素数，并输出所有素数。 */class Demo{private Demo(){}private static Demo instance = null;private int count = 0;public static synchronized Demo getInstance(){if(instance == null)instance = new Demo();return instance;}public void judgeSuShu(int integer){if (integer == 2){printFunction(integer+"\tis Su Shu");this.count++;return;}if ((integer & 0b0000_0001 ) == 0)//if (integer % 2 == 0){return;}int i = 3;while ( i <= Math.sqrt(integer)  ){if (integer %i == 0)return;elsei += 2;}count++;printFunction(integer+"\tis Su Shu");} private void showError(int integer){System.out.println("输入值:"+integer+"必须为大于或等于2的自然数！"); System.exit(0);}private void printFunction(Object obj){System.out.println(obj.toString());}public int getCount(){return this.count;}}class MainClass {public static void main(String[] args) {Demo d = Demo.getInstance();for(int i = 2; i <= 100; i++){d.judgeSuShu(i);}System.out.println("个数总计："+d.getCount());}}/*;*/